The recent comprehensive review of Maccoa Duck Oxyura maccoa biology by Clark (1964) has provlded the first detailed summary of the species' reproductive behaviour patterns and other aspects of breeding in this little-studied stiff-tail. It has been evident that the evolutionary relationships of the Maccoa Duck to the other southern hemisphere stiff-tails and the northern species of Oxyura are still uncertain at best, as evidenced by the varied taxonomic treatment that the Maccoa has received from Delacour and Mayr (1945), who regarded it as a race of O. australis, from Boetticher (1952), who consldered it as a race of O. jamaicensis, and from Delacour (1959), who finally concluded that it represents a distinct species. There can be little doubt that the last approach is most realistic, but the question still remains as to which of the other species of Oxyura the Maccoa is most closely related. In 1961 I suggested that the Argentine Ruddy Duck O. vittata, the Australian Blue-billed Duck O. australis and the Maccoa Duck comprised an evolutionary group distinct from the other forms of Oxyura. Additional evidence supporting this view has since been summarized (Johnsgard 1967), when a comparison of male display patterns of the stiff-tails was undertaken. This survey was an admittedly preliminary one, since the author had never had an opportunity to study the displays of certain stiff-tails, including the Maccoa, and published descriptions were necessarily relied upon. Recently, unpublished notes, cine films, and other information on the Maccoa had been made available, and it has become increasingly apparent that the Maccoa is a species of unusual interest.
Available at: http://works.bepress.com/paul_johnsgard/304/